Examples... Illumination sequences...

Sinus Iridum


Description


Lighting patterns on the Moon are in some sense a cosmic sundial, with each position of the Sun producing a definite pattern. Ordering a series of photos according to the sun angle should establish where other photos fall in the sequence. Unfortunately the photo times reported on the internet are not always reliable, and the way the photos are processed can affect the appearance of the terminator. In particular, points of light beyond the terminator are frequently lost to underexposure.

This page shows the changing appearance of Sinus Iridum, and the surrounding hills, as a function sun angle. The appearance of Montes Jura (the hills surrounding Sinus Iridum) as they emerge out of the darkness beyond the terminator at local lunar sunrise has sometimes been informally called the "Golden Handle". It has even been said to be so prominent an effect that it can be seen by some sharp-eyed observers without optical aid. However that may be, it happens every month and can be observed through a suitably placed telescope on Earth. This page should establish the range of sun angles over which the hills around Sinus Iridum have a "handle" like appearance. For a particular observer on Earth to observe this effect, the Moon has to be above the local horizon, and the Sun below it, when this range of sun angles is occurring.

LTVT has been used to remap each of many observation to a uniform zero libration Earth-based view. A few of the photos look slightly out of sequence -- possibly due to differences of exposure or misreporting of the times -- but the general trend of emerging peaks as the Sun rises seems fairly clear.


(Click on the thumbnails below to see full-sized LTVT screenshots. In each section, the screenshots are at an identical scale and registered. To superimpose or blink between them, open them in separate browser windows or tabs. In LTVT itself, this is accomplished by running several instances of LTVT simultaneously, with one photo being displayed in each.)

George Tarsoudis Images


The original inspiration for preparing the sunrise sequence was two images by George Tarsoudis.

Although the day and minute at which they were taken was thought to have been accurately recorded, there was some question about the hour. Such questions arise because it is possible for computer systems to unwittingly change the hour. For example, in most modern versions of the Windows operating system, the computer's clock is kept synchronized to Universal Time via the internet connection. Disk files are stamped with the Universal Time at which they were recorded or modified, but for the "convenience" of the operator, those times are displayed corrected to the local time zone, including an offset for daylight savings ("summer time") during certain months of the year. This offset is applied to all universal times regardless of where the computer was located and whether daylight savings was in effect at the time the file was stamped. As a result, the clock display looks like a local time, but it may not be the same as what a local clock would have read at the time the file was recorded. This can make it very difficult for operators to determine the offset needed to correct a particular display back to the universal time normally used for reporting astronomical observations. In Windows systems, this particular problem can be solved by using the "Date and Time Properties" dialog box to temporarily select "GMT (Casablanca, Monrovia)". This will display the time stamps in Universal Time (with no correction). However problems can still arise if files are recorded on, or transferred to and from, external media like portable drives, flash drives, and CD-ROMs. Such devices sometimes stamp files in local time, which can then be misinterpreted as a Universal Time when they are transferred to a hard drive.

Whatever the reason, the question was where these two photos fit in the sunrise sequence. The sun angle increases by about 0.35° for each 1 hour change.

George's images are shown here:

2008 May 15
2008 Jan 18
external image SinusIridum-5_14.JPG?size=64
external image SinusIridum-5_45.JPG?size=64

Sunrise Sequence at 10X


Like George's images shown above, all the following images have been remapped to zero libration views with an LTVT Zoom of 10. The numbers above each thumbnail are the sun angles calculated at 31.5°W/ 44.1°N (the IAU center of Sinus Iridum, which is also at the center of each screenshot) based on the stated time of the photo.

0.42 @ 89.6°
0.85 @ 90.8°
0.90 @ 91.8°
0.98 @ 92.9°
1.25 @ 91.2°
1.96 @ 93.3°
2.20 @ 93.0°
2.51 @ 94.6°
external image SinusIridum-0_42.JPG?size=64
external image SinusIridum-0_85.JPG?size=64
external image SinusIridum-0_90.JPG?size=64
external image SinusIridum-0_98.JPG?size=64
external image SinusIridum-1_25.JPG?size=64
external image SinusIridum-1_96.JPG?size=64
external image SinusIridum-2_20.JPG?size=64
external image SinusIridum-2_51.JPG?size=64

2.54 @ 90.7°
2.67 @ 90.4°
3.15 @ 95.1°
3.19 @ 91.6°
3.74 @ 95.7°
4.45 @ 92.6°
4.98 @ 96.0°
5.73 @ 97.6°
external image SinusIridum-2_54.JPG?size=64
external image SinusIridum-2_67.JPG?size=64
external image SinusIridum-3_15.JPG?size=64
external image SinusIridum-3_19.JPG?size=64
external image SinusIridum-3_74.JPG?size=64
external image SinusIridum-4_45.JPG?size=64
external image SinusIridum-4_98.JPG?size=64
external image SinusIridum-5_73.JPG?size=64

6.04 @ 98.0°
7.27 @ 98.0°
7.48 @ 99.3°
7.84 @ 99.8°
7.86 @ 99.8°
8.16 @ 97.1°
8.91 @ 96.5°
9.58 @ 99.4°
external image SinusIridum-6_04.JPG?size=64
external image SinusIridum-7_27.JPG?size=64
external image SinusIridum-7_48.JPG?size=64
external image SinusIridum-7_84.JPG?size=64
external image SinusIridum-7_86.JPG?size=64
external image SinusIridum-8_16.JPG?size=64
external image SinusIridum-8_91.JPG?size=64
external image SinusIridum-9_58.JPG?size=64

10.15 @ 101.9°
12.93 @ 103.1°
14.63 @ 105.2°
22.30 @ 113.8°
29.35 @ 125.8°
31.92 @ 130.3°
34.90 @ 134.6°
44.68 @ 195.0°
external image SinusIridum-10_15.JPG?size=64
external image SinusIridum-12_93.JPG?size=64
external image SinusIridum-14_63.JPG?size=64
external image SinusIridum-22_30.JPG?size=64
external image SinusIridum-29_35.JPG?size=64
external image SinusIridum-31_92.JPG?size=64
external image SinusIridum-34_90.JPG?size=64
external image SinusIridum-44_68.JPG?size=64


Images Displayed


The following table gives the observational details of the images used. The altitude (above the horizontal) and azimuth (measured clockwise from lunar north) of the Sun have been computed as they would be seen by an observer at the IAU center of Sinus Iridum (selenographic longitude/latitude 31.5°W/ 44.1°N). This is not a perfect measure of the lighting at every point, but it should be a pretty good one. For a particular solar altitude, peaks in the northern part of the Montes Jura will be slightly favored (brighter than normal) when the Sun's azimuth has a low value (sunrise terminator twisted counterclockwise), while those in the southern part will be slightly favored under the opposite circumstances.

Altitude
Azimuth
Photographer
Date
Time (UT)
Location
0.4°
89.6°
Henrik Bondo
2007 Mar 28
22:19
Fensmark, Denmark
0.8°
90.8°
Helmut Groell
2008 Feb 16
19:39
Moers, Germany
0.9°
91.8°
Albino Carbognani
2005 Mar 20
19:36
Parma, Italy
1.0°
92.9°
Mario Weigand
2007 Dec 19
17:33
Offenbach, Germany
1.2°
91.2°
Oliver Pettenpaul
2008 Feb 16
20:45
Germany
2.0°
93.3°
Howard Eskildsen
2007 Jan 29
02:02
Ocala, FL
2.2°
93.0°
Mario Weigand
2005 Mar 20
23:10
Alps, France
2.5°
94.6°
Achille Giordano
2005 Jan 20
21:50
Naples, Italy
2.5°
90.7°
Dave Nash
2004 Jun 27
22:33
Cambridgeshire, UK
2.7°
90.4°
Marco Sellini
2005 Jul 16
18:50
Italy
3.2°
95.1°
?
2005 Dec 11
16:51
Welzheim, Germany
3.2°
93.6°
?
2006 Oct 02
19:55
Malta
3.7°
95.7°
Henk Bril
2005 Dec 11
18:30
Netherlands
4.4°
92.6°
Fabio Acquarone
2007 Apr 27
20:34
Carmagna, Italy
5.0°
96.0°
Michel LeGrand
2008 Sep 10
19:35
Pic de Chateaurenard, France
5.1° ?
92.8°
George Tarsoudis
2008 May 15
18:49 ?
Alexandroupolis, Greece
5.4° ?
96.4°
George Tarsoudis
2008 Jan 18
19:27 ?
Alexandroupolis, Greece
5.7°
97.6°
H. Fukushima
1996 Jul 26
10:51
Tokyo
6.0°
98.0°
H. Fukushima
1998 May 07
08:26
Tokyo
7.3°
98.0°
H. Fukushima & Y. Sato
2001 Jun 02
13:00
Tokyo
7.5°
99.3°
?
2004 Dec 22
20:39
Hungary (?)
7.8°
99.8°
CLA Plate B15
1967 Jan 22
03:27:30
Catalina Observatory, AZ
7.9°
99.8°
CLA Plate A13
1967 Jan 22
03:30:48
Catalina Observatory, AZ
8.2°
97.1°
Henrik Bondo
2007 Mar 29
19:34
Fensmark, Denmark
8.9°
96.5°
George Tarsoudis
2007 May 27
19:50
Alexandroupolis, Greece
9.6°
99.4°
Jan Timmermans
2008 Feb 17
19:42
Netherlands
10.2°
101.9°
Christian Arsidi
2007 Dec 20
19:00
Vernouillet, France
12.9°
103.1°
Dave Nash
2007 Feb 28
21:09
Cambridgeshire, UK
14.6°
105.2°
CLA Plate B16
1966 May 02
03:49:54
Catalina Observatory, AZ
22.3°
113.8°
CLA Plate B18
1965 Dec 06
05:07:00
Catalina Observatory, AZ
29.4°
125.8°
Henrik Bondo
2007 Jan 02
21:09
Fensmark, Denmark
31.9°
130.3°
Mario Weigand
2006 Jan 13
22:17
Offenbach, Germany
34.9°
134.6°
CLA Plate aiii
1965 Jan 17
07:25:18
Flagstaff, AZ
44.7°
195.0°
AstronoMinsk Imagers
2008 Aug 19
22:52
Minsk, Russia

Here is a URL list for the amateur images:

  • file:Sinus_Iridum_URL_List.txt (not yet available)

And here are LTVT calibrations for them:

  • file:Sinus_Iridum_LTVT_CalibrationData.txt (not yet available)

These two files can be used with the LTVT Image Grabber to retrieve copies from the internet. Calibration and source information for the Consolidated Lunar Atlas plates are available elsewhere on this site.




This page has been edited 5 times. The last modification was made by - JimMosher JimMosher on Feb 22, 2009 1:53 pm